4,898 research outputs found
Josephson -state in superconductor-Luttinger liquid hybrid systems
Josephson current through a Luttinger liquid (LL) under a magnetic field is
theoretically studied. We derive an analytical expression of Josephson current
for clean interfaces, by using quasiclassical Green's function and functional
bosonization procedure. We show that critical currents can be renormalized by
electron-electron interactions at perfect transparency when LL is adiabatically
connected with superconductors. We also find that a generation of -state,
due to spin-dependent energy shift in Andreev bound states (ABS), is prohibited
even at zero temperature when the strength of repulsive interactions reaches
some critical value. The suppression of -state is caused by the low energy
fluctuations propagating in LL, and making the Zeeman splitting in ABS blurred.Comment: 5 pages, 4figure
Shadow on the wall cast by an Abrikosov vortex
At the surface of a d-wave superconductor, a zero-energy peak in the
quasiparticle spectrum can be observed. This peak appears due to Andreev bound
states and is maximal if the nodal direction of the d-wave pairing potential is
perpendicular to the boundary. We examine the effect of a single Abrikosov
vortex in front of a reflecting boundary on the zero-energy density of states.
We can clearly see a splitting of the low-energy peak and therefore a
suppression of the zero-energy density of states in a shadow-like region
extending from the vortex to the boundary. This effect is stable for different
models of the single Abrikosov vortex, for different mean free paths and also
for different distances between the vortex center and the boundary. This
observation promises to have also a substantial influence on the differential
conductance and the tunneling characteristics for low excitation energies.Comment: 5 pages, 5 figure
Boundary resistance in magnetic multilayers
Quasiclassical boundary conditions for electrochemical potentials at the
interface between diffusive ferromagnetic and non-magnetic metals are derived
for the first time. An expression for the boundary resistance accurately
accounts for the momentum conservation law as well as essential gradients of
the chemical potentials. Conditions are established at which spin-asymmetry of
the boundary resistance has positive or negative sign. Dependence of the spin
asymmetry and the absolute value of the boundary resistance on the exchange
splitting of the conduction band opens up new possibility to estimate spin
polarization of the conduction band of ferromagnetic metals. Consistency of the
theory is checked on existing experimental data.Comment: 8 pages, 3 figures, designed using IOPART styl
A Discrete Version of the Inverse Scattering Problem and the J-matrix Method
The problem of the Hamiltonian matrix in the oscillator and Laguerre basis
construction from the S-matrix is treated in the context of the algebraic
analogue of the Marchenko method.Comment: 11 pages. The Laguerre basis case is adde
Inelastic Decay of Electrons in the Shockley-type Metal-Organic Interface States
We present a theoretical study of lifetimes of interface states (IS) on
metal-organic interfaces PTCDA/Ag(111), NTCDA/Ag(111), PFP/Ag(111), and
PTCDA/Ag(100), describing and explaining the recent experimental data. By means
of unfolding the band structure of one of the interfaces under study onto the
Ag(111) Brillouin zone we demonstrate, that the Brillouin zone folding upon
organic monolayer deposition plays a minor role in the phase space for electron
decay, and hence weakly affects the resulting lifetimes. The presence of the
unoccupied molecular states below the IS gives a small contribution to the IS
decay rate mostly determined by the change of the phase space of bulk states
upon the energy shift of the IS. The calculated lifetimes follow the
experimentally observed trends. In particular, we explain the trend of the
unusual increase of the IS lifetimes with rising temperature.Comment: 8 pages, 5 figure
Magnetic interference patterns in long disordered Josephson junctions
We study a diffusive superconductor - normal metal - superconductor (SNS)
junction in an external magnetic field. In the limit of a long junction, we
find that the form of the dependence of the Josephson current on the field and
on the length of the junction depends on the ratio between the junction width
and the length associated with the magnetic field. A certain critical ratio
between these two length scales separates two different regimes. In narrow
junctions, the critical current exhibits a pure decay as a function of the
junction length or of the magnetic field. In wide junctions, the critical
current exhibits damped oscillations as a function of the same parameters. This
damped oscillating behavior differs from the Fraunhofer pattern typical for
short or tunnel junctions. In wide and long junctions, superconducting pair
correlations and supercurrent are localized along the edges of the junction.Comment: 9 pages, 4 figures, minor modifications corresponding to the
published versio
Constructive solution of highly effective photoenergy module: development and experimental testing
Based on experimental study and computermodeling of working temperature influence on the efficiency of Chinese production silicon solar cells identified temperature dependence of efficiency shows the feasibility of using Chinese production Si-SC in the construction of photovoltaic thermal system, which together with the heat pump is part of a combined system for hot water supply, heating and air conditioning. Based on a detailed analysis of the working temperature influence on the efficiency of photovoltaic processes that determine the solar cells work, it has been developed the optimal construction and technological solution of hybrid solar generated module, the main feature ofwhich is the heat exchange block, designed to reduce the solar cells working temperature. The experimental testing of hybrid modules samples equipped with developed cooling system, high-voltage part of power take-off system demonstrates their reliability and high efficiency which allow to achieve the such module efficiency up to 18.5 %.На основе экспериментального исследования в комплексе с компьютерным моделированием влияния рабочей температуры на эффективность кремниевых солнечных элементов китайского производства выявлена температурная зависимость их эффективности. Температурная зависимость показывает целесообразность использования солнечных элементов китайского производства в составе фотоэлектрической тепловой системы, которая вместе с тепловым насосом является частью комбинированной системы горячего водоснабжения, отопления и кондиционирования воздуха. На основе детального анализа влияния рабочей температуры на
эффективность фотоэлектрических процессов, определяющих работу солнечных элементов, было разработано оптимальное конструктивно-технологическое решение гибридного солнечного генерирующего модуля, основной особенностью которого является теплообменный блок, предназначен для снижения рабочей температуры солнечных элементов. Экспериментальные испытания образцов таких модулей, оснащенных разработанной системой охлаждения и высоковольтной системой отбора мощности, демонстрируют их надежность и высокую эффективность, позволяющие достичь КПД гибридного модуля до 18,5 %
Point Contact Spectroscopy of Superconducting Gap Anisotropy in Nickel Borocarbide Compound LuNi2B2C
Point contacts are used to investigate the anisotropy of the superconducting
energy gap in LuNi2B2C in the ab plane and along the c axis. It is shown that
the experimental curves should be described assuming that the superconducting
gap is non-uniformly distributed over the Fermi surface. The largest and the
smallest gaps have been estimated by two-gap fitting models. It is found that
the largest contribution to the point-contact conductivity in the c direction
is made by a smaller gap and, in the ab plane by a larger gap. The deviation
from the one-gap BCS model is pronounced in the temperature dependence of the
gap in both directions. The temperature range, where the deviation occurs, is
for the c direction approximately 1.5 times more than in the ab plane. The
\Gamma parameter, allowing quantitatively estimate the gap anisotropy by
one-gap fitting, in c direction is also about 1.5 times greater than in the ab
plane. Since it is impossible to describe satisfactorily such gap distribution
either by the one- or two-gap models, a continuous, dual-maxima model of gap
distribution over the Fermi surface should be used to describe
superconductivity in this material.Comment: 10 pages, 14 Figs, accepted in PR
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